The
            <i>Bradyrhizobium japonicum nolA</i>
            Gene Encodes Three Functionally Distinct Proteins

Loh, John T.; Stacey, Minviluz G.; Sadowsky, Michael J.; Stacey, Gary

doi:10.1128/jb.181.5.1544-1554.1999

Cited by 32 publications

(22 citation statements)

References 55 publications

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“…Similarly, the nolA gene of Bradyrhizobium japonicum gives multiple gene products from internal translational starts [112]. Three proteins are produced, only the ¢rst of which, NolA 1 , contains the helix-turn-helix DNA binding motif and it regulates the expression of NolA 2 and NolA 3 as well as acting at the nolD promoter [113].…”

Section: Thoughts On the Evolution Of Merr-like Regulatorsmentioning

confidence: 99%

The MerR family of transcriptional regulators

et al. 2003

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The MerR family is a group of transcriptional activators with similar N-terminal helix-turn-helix DNA binding regions and C-terminal effector binding regions that are specific to the effector recognised. The signature of the family is amino acid similarity in the first 100 amino acids, including a helix-turn-helix motif followed by a coiled-coil region. With increasing recognition of members of this class over the last decade, particularly with the advent of rapid bacterial genome sequencing, MerR-like regulators have been found in a wide range of bacterial genera, but not yet in archaea or eukaryotes. The few MerR-like regulators that have been studied experimentally have been shown to activate suboptimal sigma(70)-dependent promoters, in which the spacing between the -35 and -10 elements recognised by the sigma factor is greater than the optimal 17+/-1 bp. Activation of transcription is through protein-dependent DNA distortion. The majority of regulators in the family respond to environmental stimuli, such as oxidative stress, heavy metals or antibiotics. A subgroup of the family activates transcription in response to metal ions. This subgroup shows sequence similarity in the C-terminal effector binding region as well as in the N-terminal region, but it is not yet clear how metal discrimination occurs. This subgroup of MerR family regulators includes MerR itself and may have evolved to generate a variety of specific metal-responsive regulators by fine-tuning the sites of metal recognition.

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Section: Thoughts On the Evolution Of Merr-like Regulatorsmentioning

confidence: 99%

The MerR family of transcriptional regulators

et al. 2003

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“…NodD1 activates gene expression in a flavonoid‐dependent manner (Göttfert et al ., 1992), whereas NodD2 represses transcription of nod ‐genes (Garcia et al ., 1996). NolA (a regulator of the MerR type) upregulates nodD 2 in a quorum‐sensing‐dependent way, and also acts as a feedback‐regulator of the biosynthesis of Nod‐factors in B. japonicum (Loh et al ., 1999; 2001; 2002a,b; Loh and Stacey, 2001). Flavonoid‐dependent activation of nod‐ loci in B. japonicum is also controlled by the two‐component system NodV/NodW (Göttfert et al ., 1990; Loh et al ., 1997).…”

Section: Introductionmentioning

confidence: 99%

Flavonoids induce temporal shifts in gene‐expression of nod‐box controlled loci in Rhizobium sp. NGR234

Kobayashi

Naciri

Broughton

et al. 2004

Molecular Microbiology

122

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SummaryRhizobia, soil bacteria of the Rhizobiales , enter the roots of homologous legumes, where they induce the formation of nitrogen-fixing nodules. Signals emanating from both symbiotic partners control nodule development. Efficient nodulation requires precise, temporal regulation of symbiotic genes. Roots continuously release flavonoids that interact with transcriptional activators of the LysR family. NodD proteins, which are members of this family, act both as sensors of the environment and modulate the expression of genes preceded by conserved promoter sequences called nod -boxes. The symbiotic plasmid of the broad host-range Rhizobium sp. NGR234 caries 19 nod -boxes (NB1 to NB19), all of which were cloned upstream of a lacZ -reporter gene. A flavonoid, daidzein was able to induce 18 of the 19 nod -boxes in a NodD1-dependent manner. Interestingly, induction of four nod -boxes (NB6, NB15, NB16 and NB17) is highly dependent on NodD2 and was delayed in comparison with the others. In turn, NodD2 is involved in the repression of the NB8 nodABCIJnolOnoeI operon. Activation of transcription of nodD 2 is also dependent on flavonoids despite the absence of a nod -box like sequence in the upstream promoter region. Mutational analysis showed that syrM 2 (another member of the LysR family), which is controlled by NB19, is also necessary for expression of nodD 2. Thus, NodD1, NodD2 and SyrM2 co-modulate a flavonoid-inducible regulatory cascade that coordinates the expression of symbiotic genes with nodule development.

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“…Transconjugants were tested for their ability to be induced by soybean seedling extract (SSG) as previously reported by Loh et al (1999).…”

Section: Plasmidsmentioning

confidence: 99%

“…It modulates repression by positively activating nodD2 whose protein product represses transcription of the nod genes (Garcia et al, 1996). Unlike the nodulation genes, the expression of NolA is not induced by isoflavones (Loh et al, 1999). Recent studies, however, indicate that the transcription of nolA can be induced in response to chitooligosaccharide molecules present in the cell.…”

Section: Introductionmentioning

confidence: 99%

Feedback regulation of the Bradyrhizobium japonicum nodulation genes

Loh¹,

Stacey²

2001

Molecular Microbiology

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Lipochitin Nod signals are produced by rhizobia and are required for the establishment of a nitrogen‐fixing symbiosis with a legume host. The nodulation genes encode products required for the synthesis of this signal and are induced in response to plant‐produced flavonoid compounds. The addition of chitin and lipo‐chitin oligomers to Bradyrhizobium japonicum cultures resulted in a significant reduction in the expression of a nod–lacZ fusion. Intracellular expression of NodC, encoding a chitin synthase, also reduced nod gene expression. In contrast, expression of the ChiB chitinase increased nod gene expression. The chain length of the oligosaccharide was important in feedback regulation, with chitotetraose molecules the best modulators of nod gene expression. Feedback regulation is mediated by the induction of nolA by chitin, resulting in elevated levels of the repressor protein, NodD2.

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The Bradyrhizobium japonicum nolA Gene Encodes Three Functionally Distinct Proteins

Cited by 32 publications

References 55 publications

The MerR family of transcriptional regulators

The MerR family of transcriptional regulators

Flavonoids induce temporal shifts in gene‐expression of nod‐box controlled loci in Rhizobium sp. NGR234

Feedback regulation of the Bradyrhizobium japonicum nodulation genes

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